Immune System

Third Line of Defense – Specific Immunity

called into action when nonspecific methods are not enough and infection becomes widespread

FUNCTION mounts attacks against

specific foreign substances

specific foreign

substances

FEATURES………………

Self/non-self discrimination - it normally distinguishes between self and non-self and only reacts against non-self.

non-self

When a nonself (foreign) body is detected, mitotic activity in B and T lymphocytes is stimulated

While mitosis is occurring, the daughter populations become subdivided into…

Effector cells when fully differentiated,

they will seek and destroy foreign materials

Memory cells

become dormant, but can be triggered to rapid mitosis if pathogen encountered again

Memory - it demonstrates memory. The immune system "remembers" if it has seen an antigen before and it reacts to secondary exposures to an antigen in a manner different than after a primary exposure. Generally, only an exposure to the same antigen will trigger this memory response.

Specificity - there is a high degree of specificity in its reactions. A response to a particular antigen is specific for that antigen or a few closely related antigens.

CELLS INVOLVED

………………

Macrophages engulf foreign objects inform T lymphocytes at a

specific antigen is present

Helper T cells

produce and secrete chemicals which promote large numbers of effector and memory cells

Cytotoxic T cell T lymphocytes

that eliminate infected body cells and tumor cells

B Cells produce antibodies (secrete them

in the blood or position them on their cell surfaces)

The process can be simplified into three

events:

(1) Recognition of a specific invader

SPECIFIC INVADER

(2) Repeated cell divisions that form huge lymphocyte populations

(3) Differentiation into subpopulations of effector and memory cells

Effector Memory